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Old 04-08-2003, 03:36 PM   #6
sck
 
Join Date: Mar 2003
Thumbs up The Wonderful World of SCUBA

Major props to Killer Kat and Crick, they helped me understand this all in the first place.

In the last few weeks/months, there has been a preponderance of questions regarding the utilization of SCUBA tanks in filling HPA bottles. Thus, I am authoring this post (by request) in an attempt to enlighten, clarify and resolve any misunderstanding or misgivings you may have in regards to the use of SCUBA tanks. While I do not claim to be an authority or expert in this field, I believe my experience more than qualifies me to give an introduction to those that lack basic knowledge concerning SCUBA tanks. While this post will not shed any new light for paintball vets, it will hopefully be informative to those new to the game, HPA, or SCUBA tanks.


BASIC INFORMATION

SCUBA tanks are gauged not only by psi, but their basic size. More specifically, they are measured in Cubic Feet (cu. ft.) The most commonly used SCUBA tanks are 3000 psi/80 cu. ft. (there are other sized tanks available, but the 80 is definitely the way to go in terms of value.) While there are 4500 psi tanks available, they have tendency to be inconveniently bulky, and more importantly, three to five times more expensive than their 3000 psi counterpart.

While I cannot be sure, I would assume SCUBA tanks are fairly universal in size. I have two 80 cu. ft. tanks, one new, one used. They are both 30¨ in height, 7.5 inches in diameter and weight approximately 45 pounds when full. They fit easily into the backseat of my car (though I drive a big old man car!!)


GETTING STARTED

FILL STATION: Before you even get a SCUBA tank, you will need a fill station. The fill station is used to connect the SCUBA tank to your HPA bottle; a SCUBA tank is worthless to a paintballer without a fill station. These are very common and easy to find. You can find them at most local pro-shops and online paintball retailers. They can range from anywhere from $40-$80. I have the cheap $40 variety and notice no difference to a nicer fill station.

SCUBA TANK(s): As previously stated, I recommend an 80 cu. ft. tank. You can find them at Paintball websites/stores, EBay, some sporting goods websites (e.g. sportschalet.com), and/or local dive shops. I would not pay more than $110 for a NEW tank. I actually paid $80 for a used tank at a local dive shop. The tank has to have a "K-valve¨ (I believe that is the name) so it is compatible with a fill station. Most dive shops have probably dealt with paintballers, so theyˇ¦ll know how to direct you. I bought both of my SCUBA tanks off the shelf, ready to go, so I donˇ¦t think valve compatibility should be an issue. I like supporting small business (sorry to get political) so I recommend you go to the dive shop. They will probably be the people filling your tank to begin with, so it doesn't hurt getting on their good side and supporting them! I have one new and one used tank, though since hindsight is 20/20, I just assume buying USED tanks.

AIR FILLS: This can sometimes be complicated. I've found that while many people are willing to sell you a SCUBA tank, they're not nearly as cooperative in filling them. Many vendors require a C-Card or diving certification in order to fill your tanks. BE SURE TO CALL AROUND AND MAKE SURE YOU CAN GET YOUR TANK(s) FILLED BEFORE MAKING AN INVESTMENT!!! If and when you do find someone that fills tanks, I would recommend buying your tanks from them assuming the price is decent. I pay $4.00 to fill one 80 cu. ft. tank.
--When getting your tanks filled, always make sure to bring your fill station and top off your bottle. This will require them to fill the SCUBA tank, top off your bottle, and then top off the SCUBA tank AGAIN (thatˇ¦s why you want to get on their good side.) This way, when you leave you will have a full HPA bottle and SCUBA tank. In my opinion, this is very important in conserving the air in your SCUBA tank. You will see why in the following sections.


USING A SCUBA TANK

Setting up and using a SCUBA tank is an easy and self-explanatory task, hence I prefer not cover it. Nonetheless, I will pay it heed. On all fill stations, one end contains an OPENING and SCREW to attach to the SCUBA tank. The other end has a nozzle piece that attaches to your HPA bottle. On the side of the fill station, there is a release valve. It will all make sense when you see the pieces.

1. Screw the fill station onto the SCUBA tank
2. Close the release valve (if it isnˇ¦t closed already)
3. Attach HPA bottle to nozzle portion of fill station
4. SLOWLY, open the valve to the SCUBA tank. For best efficiency, always fill your bottle slowly. Going too quick excites the gas, thus pressurizing the bottle too rapidly, and will not let allow you to reach the potential maximum psi.
5. The SCUBA tank will STOP filling on its own.*
6. Close the valve to the SCUBA tank
7. Open the release valve
8. Remove your HPA bottle from the fill station
9. Remove your fill station from your SCUBA tank

*Initially, your HPA bottle will fill up to 3000psi; however it will drop with subsequent fills. Essentially, the SCUBA tanks quits filling when it can no longer project air into the HPA bottle because it lacks the internal pressure. The MOMENT you release air out of your full SCUBA tank, it looses internal pressure. The more air you release, the more pressure you release. I will devote more on this in the next section.


AIR CONSUMPTION/PRESSURE LOSS

ONE 80 cu. ft. tank WILL ONLY YIELD ONE OR TWO 3000 psi FILLS!!

You did not misread that, ONE FULL SCUBA TANK will only FILL your tank a couple of times. A SCUBA tank doesnˇ¦t have enough pressure to go over 3000 psi, so in reality, the fill is closer to 2800 once the air settles. Following that, EACH fill will lose approximately 100-250 psi/fill, because as stated earlier, the SCUBA tank lacks the internal pressure to do so. Sorry to sound like a broken record, but remember, the MOMENT you release air out of your full SCUBA tank, it looses internal pressure. Thatˇ¦s why there is that 100-250psi drop off between fills!!!

Example: Utilizing ONE tank

Number of fills PSI (of both tanks, before settling)
1 3000
2 2800
3 2750
4 2550
5 2300
6 2150

As you can see, with each fill, the SCUBA tank becomes less and less pressurized, and thus looses its ability to fill an HPA bottle. Obviously, the more you gas up, the more pressure you use. Thus, I recommend topping off as often as possible. It is less taxing on the tank to go from 1700 to 2800psi opposed to 600 to 2800psi. Actually, I just hate shooting with less than 1000psi so thatˇ¦s why I probably recommend it!!


CASCADING: Cascading is a way to get around the pressure limitations of a single SCUBA tank. You will need at least TWO tanks to utilize this method. This way, you would use one tank(s) as the primary fill tank, and the another tank exclusively to top off. This way, while one tank loses pressure at a rapid rate; the other remains relatively full, enabling it to keep filling at a higher psi.

Example: Utilizing TWO tanks

Fills-- PSI/SCUBA #1-- PSI/SCUBA #2, HPA bottle
1 2400 3000
2 2300 3000
3 2200 2900
4 2100 2850
5 1950 2700
6 1800 2550

Example: Utilizing THREE tanks
Fills-- PSI/SC#1-- PSI/SC#2-- PSI/SC#3, HPA--
1 1500 2500 3000
2 1450 2400 3000
3 1350 2300 3000
4 1300 2250 2900
5 1250 2200 2800
6 1150 2100 2700

Thus, as you can see, the more SCUBA tanks you have, the longer you can stay at a high PSI. The numbers listed above are NOT scientifically researched, rather, a rough approximation to illustrate how cascading works.

4500 and 5000psi HPA bottles CAN be filled with a SCUBA tank, however they will only get up to 3000 psi.

One scuba tank is more than enough for one person, assuming you just shoot a case (or two) a day . I have two because I have a tendency to be excessive, and because I share with friends (they always kick in for the fills.) I also like going into a game with over 2500psi in my tank! I go through AT LEAST a case and half a day as well. I went out both Saturday and Sunday last weekend, and the tanks sufficed for the entire weekend (though I was not happy with them by Sunday afternoon!)

Well, I hope this helpful for some of you! I love my SCUBA tanks and encourage anyone who is thinking about it to make that investment. As long as you play regularly, the purchase will eventually pay for itself over time.

Last edited by BourneKiller : 04-15-2003 at 03:11 PM.
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